Replacing an outer chainring
 

I'm taking some components off a '04 Marlin that was run over by a car and putting them on a '97 Marlin frame. When I took my bike to the local shop one of the guys told me the outer chainring on my crankset was tweaked from being run over--it needs to be replaced. I'm new to bike mechanics so I have a lot of questions about this.

1) The crankset I transfered over is a "Bontrager Select, 22/32/42 teeth" according to Bikepedia. Do I need to get a new outer chainring with the same # of teeth?

2) I've noticed most of the chainrings available on line are for 9 and 10 speed drivetrains. I wanted to use the rear cogs from my totaled '04 Marlin, which Bikepedia lists as "8-speed, 11 - 32 teeth". I've noticed most of the chainrings available on line are for 9 and 10 speed drivetrains. Will an outer chainring (and possibly middle one, too) listed as being for a 9 to 10 speed drivetrain work with my casette? I've done some on line research regarding this and there seems to be some disagreement. Apparently the bolt size and chain size are important factors?

3) Assuming that I can replace outer chainring with one listed as being for 9 speeds, will my old shifters (the ones from the '04 Marlin that accompanied the 8 speed drivetrain) work okay?

Thank you for your time.

8s and 9s rings are generally the same, so you should be OK. You can also change the size if you prefer. If you change size or brand, you may lose the "hyper" or the "glide" because in the exact position of the shift gates, but it'll work fine, and you may not notice any material change.

Check your crankset carefully to ensure that it was only the outer chainring that was damaged and not the spider as well. If the chainring is steel it can probably be bent back into shape, but if you decide to replace it you will need to match the bolt circle diameter (BCD) and number of bolts, of course, and you can change the number of teeth somewhat if you wish.

If you go larger you may have a problem with the chain rubbing on the inside of the big chainring while on the middle ring and smaller rear cogs; there are spacers available which can be used to move it outwards. I recently had this issue going from 42 to 46 teeth and a 1.2mm spacer cleared it up. Whatever you do, expect to have to readjust the front derailleur somewhat. I suggest starting from scratch.

If you change the number of teeth you will probably need to readjust the derailleur height as well. If you run into roughness shifting into the big ring you may find that rotating the chainring to a different position on the spider may "phase" it differently with the middle ring; you may find a "sweet spot" at one particular position.

I'm not familair with that particular crank but are the chainrings bolted on or riveted? If they are riveted, you cannot change them but must replace the entire crank. If they are bolted on, you must match the bolt circle and number of bolts as mentioned above.

Also make sure you have enough clearance from the chain stay if going to a larger ring.

The rear shifter needs to match the number of cogs (speeds) in the rear, 8 to 8, 9 to 9, 10 to 10, etc.

I ended up purchasing an (http://www.chainreactioncycles.com/M...?ModelID=82820) E Thirteen Triple Shiftring kit to replace my current chain rings. I didn't realize I had to make sure it would be compatible with my existing cranks. The middle chain ring from this kit does not fit on the crank. Is it a big deal if I use my old middle chain ring and the 2 new E Thirteen inner and outer chain rings which seem to fit just fine?